The present invention relates to a sanitary napkin provided with wings and more particularly to a women""s sanitary napkin provided with wings having a tension relief means.
As known in the art, women""s sanitary napkins are generally disposable and used to collect and contain vaginal exudates, especially menstrual blood and intermenstrual secretions.
Such napkins are usually comprised of a substantially flat oblong absorbing core wrapped by a top layer and a lining layer. The top layer contacts the pelvic region of the user and is usually made of permeable material that does not cause any irritation to the skin. The purpose of the lining layer, which is generally made of impervious material and opposite the top layer, is to prevent the collected fluid retained in the napkin core from touching the user""s clothes.
The attachment of the sanitary napkin to the lingerie is generally attained through adhering regions in the lining layer that are stuck to the user""s undergarment.
The materials of the top layer, lining layer, napkin core, and the types of adhesive are fully known by one skilled in the art.
Currently, a great number of women""s sanitary napkins are provided with flexible wings that extend laterally from the sides of the napkin core and are adapted to be folded over a crotch portion of the wearer""s undergarment. The wings may be formed as a prolongation of one or both said lining and top layers, or alternatively, may be formed from separate layers which are affixed to the napkin. Said wings perform at least two functions: they fix said napkin to the user""s undergarment, thus preventing same from displacing therefrom, and prevent the exudates from leaking through the sides of the napkin. Those two functions contribute to a reduction in the occurrence of stains in the user""s clothes.
During the use of a napkin provided with side wings, the latter are folded around the edges of the portion of the undergarment to be lodged between the user""s thighs, being attached to the external face thereof. Preferably, one or more surfaces of said wings have adhesive coated regions, thus promoting the attachment to the external face of the undergarment and preventing the napkin from being displaced while in use.
While napkins provided with side wings are normally seen as more efficient than the ones without side wings for the attachment to undergarment, there still exist problems with current wing designs. Foe example, occasionally the wings become unattached from the undergarment due to the stresses to which they are submitted while in use. As the wings are folded over the edges of the undergarment while in use, stresses occur which are especially high along the folding line which is curved since it runs along the edges of the crotch portion of the undergarment to be lodged between the user""s thighs. Such stresses increase as the user moves, for example, by walking or crossing her the legs, at which time the edges of the undergarment are pulled against the wings of the napkin, thus increasing-the stress against the folding line. The stress increases to a level wherein the wing becomes unattached from the undergarment, thus eliminating the advantages attained by this way of attaching the napkin thereto.
Despite the difficulty in assuring the absolute integrity of a napkin, as well as its fixation at a certain position, in view of the anatomy of the user and her movements, the conception of napkins that at least reduce the above-mentioned problems has been a constant worry.
The technique prior to the present invention is prodigal in expedients for solving such problems, some of which were described in documents WO 93/06805, WO 95/03022, WO 96/14816, WO 96/10977, WO 97/12576, U.S. Pat. No. 4,917,697 and U.S. Pat. No. 4,940,462.
Such documents suggest modifying the traditional wings such as by changing their surface thus allowing same to extend more, including undercuts and folds, or providing multiple overlapped elements. The purpose of all these disclosures is to have the wing itself as the tension relief means. However, this makes the structure of the wing more complex, more expensive, or more inconvenient to the user.
An object of the present invention is to provide a sanitary napkin provided with wings which is simple and efficient in preventing the wings from becoming unattached from the undergarment when in use.
Another object of the present invention is to provide a sanitary napkin provided with wings and tension relief structures which are not located in the respective wing folding zones, but rather in the focal points of undesirable stresses, that is, the points where said wings are attached to the external face of the undergarment, generally by means of an adhesive.
Still one another object of the present invention is a sanitary napkin provided with wings and a tension relief structure which is similar to the traditional product the user is familiar to and does not require special manipulation, different from the one currently used.
Such objects are attained by a sanitary napkin provided with side wings wherein at least one of said wings is provided with a tension relief structure, thus associating, during the use, said wing with the user""s undergarment.
In accordance with the present invention, there has been provided a sanitary napkin comprising a body faceable liquid permeable top layer, a garment faceable liquid impermeable lining layer and an absorbing core intermediate the top layer and the lining layer, the sanitary napkin further including a flexible wing adapted to be folded over a crotch portion of a wearer""s undergarment in use, wherein said wing is provided with a tension relief structure, the tension relief structure having first surface affixed to a garment faceable surface of the wing and a second surface that is adapted to contact the undergarment in use, the second surface being movable with respect to the first surface and the second surface having an adhesive region that releasably adheres the tension relief structure to the user""s undergarment.
As used in this context, the terminology xe2x80x9ca tension relief structurexe2x80x9d means a physical arrangement, for example, a flexible form provided with a certain volume which is not integral with the continuous surface of the wing itself The present invention is not intended to include wing structures wherein tension relief is provided by replacing the conventional material within the wing with a material this is capable of being stretched and distorted when submitted to stresses, nor does it include cuts or slits in the wings, or changes in the profile thereof such as by ring rolling or similar techniques.
Preferably, the tension relief structure is permanently adhered to the surface of the wing in such a way that, during the use of the absorbing article, it folds and turns onto the external face of the region of the undergarment to be lodged between the user""s thighs. And the tension relief structure associates the wing with the user""s undergarment, thus preferably providing a non-permanent adhesion between them, for example, by a pressure sensitive adhesive usually known as PSA.
Typical examples of the tension relief structure are hollow or non-hollow spatial arrangements provided or not with continuous surfaces made of flexible and/or elastic material, for example, in the shape of a pipe, a sphere, an angle-iron, a joint, a handle, a polyhedron, a block of foam, sponge or rubber, etc. A basic feature of the tension relief structure in accordance with the invention is that two distinct lengths of its surface, when adhered to two bodies that move independently, are able to follow such movements by distorting in such a way to prevent the association between the two bodies from being disrupted.
In other words: usually two surfaces adhered to each other (in this case the surface of the undergarment and the wing-shaped surface of a sanitary napkin), when submitted to shear forces, tend to separate when one of them slides over the other in opposite directions, until the applied force overcomes the deformation capacity of the adhesive layer and said surfaces separate from each other. When according to the invention a deformable, extensible and/or elastic structure that can suffer a certain deformation without losing the adhesion thereto is inserted between said surfaces, its capacity to keep the two surfaces joined together is increased.